The scrubbing of exhaust gases originating from energy production, from different industrial processes and the like, is becoming an increasingly important procedure because of the ever-tightening discharge standards. Such exhaust gases include, among others, flue gases generated as the result of combustion.
Flue gas scrubbers known per se can be employed for scrubbing flue gases. A flue gas scrubber is a cleaning device that separates impurities from the flue gases by the wet method. A flue gas scrubber comprises not only an actual flue gas scrubbing part, but also often also a droplet separator. Let it be mentioned that hereinafter a flue gas scrubber will referred to as “scrubber” in the present description.
Power stations are known that comprise a plurality of different flue gas sources. An example of such a station is a diesel power station comprising a plurality of engines operating by the diesel principle. A diesel power station may produce energy for instance for the needs of an industrial establishment or a community. In such power stations, the aim in most cases is to scrub the flue gases of several different engines, preferably all the engines of the power station, in one flue gas scrubber. This being so, the flue gases are conveyed from each engine along special flue gas conduits to an inlet connection, wherein the flue gas flows come into contact with each other. The gathered flue gases are conveyed from the inlet connection to the actual scrubbing process in the scrubber. FIGS. 1a to 1c show such a scrubber.
A problem in the above-described arrangement is that when the number of engines and conduits is large, the inlet connection becomes considerably large, larger than would be necessary in view of flow dimensioning. The width of the inlet connection may be even larger than the width of the part of the scrubber containing the actual scrubbing means. It is naturally difficult to place such an inlet connection in such a manner that it does not cause lack of space around the scrubber.
A further problem is that because of the large flow surface area of the inlet connection the flow rate of the flue gas may remain so low in partial loading situations that the inlet connection is rapidly soiled. This shortens the service intervals of the scrubber thus causing extra costs.
When a power station comprises a plurality of diesel engines, typically at least one of said diesel engines is out of use by turns, for example during service. The flue gas conduit of said diesel engine is closed with a damper, so that flue gas originating from the other engines would not flow into said engine. If this happened, uncontrollable turbulent flows may be caused in the gas flow at the inlet connection. Turbulent flows may cause back flow from the side of the actual scrubber to the inlet connection. The back flow contains chemicals used in the scrubbing process of the scrubber, which are strongly corroding and spread out to the inner surfaces of the inlet connection. The inlet connection must therefore be made from a special material resistant to said chemicals, or at least its inner surface must be coated with such a material. Typically, feasible materials are extremely expensive. In addition, the processing thereof, welding, for example, is demanding and expensive. A large inlet connection requires a significant amount of said special materials, which makes said structure very expensive. A further problem is that the structure of a large inlet connection has to be reinforced with various heavy reinforcements, for instance large carrier beams, in order for its structure to become sufficiently rigid. Numerous reinforcements are not only expensive but they also complicate the fastening of insulators and other corresponding structures to the inlet connection. Should the scrubber be built on a seismic zone, the protective coefficients of the structures further increase the size of the reinforcements required.
The effect of fatiguing loads caused by operating vibrations and pressure shocks, which are typical of diesel engines, is difficult to foresee in a large input connection, particularly with a plurality of engines connected thereto. Furthermore, the movements and flexibilities, which are within allowed limits per se, caused by said vibrations, are large, which in its turn complicates the design of the inlet connection and the structures associated therewith. Still further, if an emergency cooling pipework is used, a reliable support and fastening thereof is difficult in an inlet connection making large movements. A further problem is that the dampers have to be adapted tightly to the inlet connection, which makes them difficult to service.